From Ask Dr Wiki
Pneumonia is the inflammation of the lungs that is usually caused by the infection with bacteria, virus, fungi or other organisms. But the term pneumonia means different to pathologists and clinicians. For pathologists it means infection of the alveoli, distal airways and interstitium that manifests as increased weight of the lungs, replacement of the normal lung’s sponginess by consolidation and alveoli filled with white blood cells, red blood cells and fibrin. For clinicians, the term pneumonia means, a constellation of signs and symptoms like fever, chills, pleuritic chest pain, sputum production, hypo or hyperthermia, tachypnea and characteristic findings like bronchial breathing on auscultation. Pneumonia mainly affects children and people of old age though even young people are also susceptible.
Pneumonia is broadly classified in to two categories based on how the infection is acquired. They are- Community Acquired Pneumonia and Hospital acquired Pneumonia or Nosocomial Pneumonia. Community acquired pneumonia in turn can be either those that be treated in an ambulatory setting or those which are very severe requiring inpatient treatment. Likewise Nosocomial pneumonia can be either ventilator associated or non-ventilator associated pneumonia.
The pulmonary host defenses that prevent infections include the anatomical features like nasal turbinates, sharp angulation of the nasopharynx, muco-ciliary transport system, and glottis. These all prevent infections at the upper respiratory tract level. Cough reflex prevent infections entering in to the lower respiratory tract. Lower respiratory tract in addition is protected by macrophages, fibronection, lyzozymes, lactoferrin, IgG and surfactants. When these defense mechanisms are disrupted, it results in pneumonia.
Infections may be acquired by aspiration, aerosolization, and hematogenous spread or by contiguity from a nearby infected site. Certain microorganisms like Chlamydia possess ciliostatic factors which disrupt the mucociliary barrier to cause infection. ]] The common organisms causing pneumonia are Streptococcus pneumonia, Staphylococcus aureus, Mycoplasma pneumoniae, Hemophilus influenza, Pseudomonas aeruginosa and Klebsiella pneumoniae.
Pneumonia manifests are four patterns which are lobar pneumonia, bronchopneumonia, interstitial pneumonia and military pneumonia.
This pneumonia classically involves the entire lobe of the lung. There are four stages – congestion, red hepatization, gray hepatization and resolution.
This consist of patchy consolidation involving one or several lobes usually the lower and the posterior lobes.
It is defined by histopathological identification of the inflammatory process predominantly involving the interstitium including the alveolar wall and the connective tissue surrounding the bronchovascular tree.
It consists of numerous discrete lesions resulting from spread of the pathogens to the lungs via the blood stream.
Signs and symptoms
Most of the people have initial symptoms of cold which is later followed by other symptoms like –
- Fever with chills
- Sputum , sometimes blood stained
- Chest pain
The diagnosis is done by history, clinical examination and investigations. Clinical examination may show fever, breathlessness, cyanosis, dullness to percussion, bronchial breathing, egophony, crackles, wheezes and pleural friction rub. The most important investigation is [category:X-ray|chest x-ray]. It may show consolidation in the form of opacity or white patches. In interstitial pneumonia, x-ray may not show anything abnormal. Pulmonary Function Tests may show a decrease in the vital capacity, lung compliance, functional residual capacity and total lung capacity. The other investigations include complete blood count, sputum examination and sometimes blood culture.
The treatment essentially consists of administration of antibiotics. Many pathogens are resistant to a number of antibiotics. So the choice of the antibiotics depends on the type of organism, its susceptibility to the antibiotics and the condition of the patient.
Severe cases of pneumonia are to be treated as inpatients with supportive care including oxygen administration, intravenous fluids and sometimes under ventilatory management.